1. Field of the Invention
The present invention generally relates to a solder ball sucking apparatus for placing, through vacuum attraction, solder balls on electrodes of electronic components such as a semiconductor chip and a circuit board and more particularly, to a solder ball attracting mask mounted on the solder ball sucking apparatus and its manufacturing method.
2. Description of the Prior Art
Conventionally, in case solder balls are placed on electrodes formed in a predetermined array on a semiconductor chip or a circuit board, a number of solder balls are sucked under vacuum at a time by a suction apparatus mounted with a solder ball attracting mask having suction holes in a predetermined pattern and then, are placed on the electrodes upon cancellation of vacuum suction after having been transferred over the electrodes as disclosed in, for example, Japanese Patent Laid-Open Publication No. 7-202401 (1995).
However, in response to higher integration of the electronic components and higher density and more complication of an array of the electrodes in recent years, an array of the solder balls is also diversified upon increase of the number of the solder balls sucked at a time by the suction apparatus, namely, the number of through-holes formed on the solder ball attracting mask and communicating with the suction apparatus also increases and an array of the through-holes becomes complicated, so that suction forces applied to the respective through-holes drop through their dispersion and thus, an error in attraction of the solder balls is likely to occur. Meanwhile, since the solder balls become so small as to have a diameter of not more than 0.5 mm, a transfer error that the solder balls are not placed on the electrodes accurately may happen due to a so-called double ball phenomenon that the solder balls are transferred in a state where a plurality of the solder balls are attracted to one through-hole.
Accordingly, an essential object of the present invention is to provide, with a view to eliminating the above mentioned drawbacks of prior art, a solder ball attracting mask mounted on a suction apparatus, in which by giving a special shape to the solder ball attracting mask, solder balls are attracted to respective through-holes securely such that an error of attraction of the solder balls and an error of transfer of the solder balls can be eliminated.
Another important object of the present invention is to provide a method of manufacturing the solder ball attracting mask efficiently by electroforming.
In order to accomplish these objects of the present invention, a solder ball attracting mask according to the present invention is mounted on a suction apparatus for sucking a plurality of solder balls under vacuum so as to place the solder balls on electrodes of an electronic component and is formed, at its predetermined positions, with a plurality of through-holes for attracting the solder balls thereto, respectively. The solder ball attracting mask has a principal face engageable with the solder balls and a rear face engageable with the suction apparatus such that the through-holes extend through the solder ball attracting mask from the principal face to the rear face. Each of the through-holes includes a funnellike attraction area for attracting the solder ball thereto, which reduces its diameter gradually from the principal face towards the rear face up to a suction port. Each of the through-holes further includes a suction hole which has a diameter larger than that of the suction port and extends from the suction port to the rear face so as to define a suction space.